1. Field of the Invention
The present invention relates generally to connecting cards in computer systems. More particularly, the present invention relates to preventing power damage to cards and other peripherals.
2. Description of the Related Art
An interface bus is a path inside a computer system for transferring data between a processor and other computer peripherals. Developed by Intel Corporation and other industry leaders in 1993, the Peripheral Component Interconnect (PCI) local bus has become the standard interface bus for high-speed devices. A conventional PCI bus includes a 64-bit bus. More typically implemented as a 32-bit data path and operating at 33 megahertz (MHz), the PCI bus boasts a maximum data transfer rate of 132 megabytes/second.
The standard PCI bus has attained market dominance, not only because of its performance capabilities, but also because of the flexibility and expandability of the PCI system. Most PCI systems support several peripherals, which may be integrated directly onto the motherboard or be added on a PCI expansion card. These PCI cards, each of which may include peripherals having multimedia, graphics, video, disk drive, or network capabilities, allow a user to customize and re-customize a computer system at any time.
A PCI system also gives a user the flexibility of removing and replacing a damaged or obsolete PCI card without replacing the entire motherboard.
A PCI card may be installed almost effortlessly into a computer system by sliding the PCI card into a PCI slot, after the power to the PCI slot has been disabled. Once a PCI card is properly installed, a xe2x80x9cplug and playxe2x80x9d feature may then be used to complete integration of the peripheral into the computer system. A PCI card may also be easily uninstalled by first disabling power to the PCI slot and then removing the PCI card. In addition, advances in the server technology have made it possible to replace cards while the system is running by disabling power only to one particular PCI slot (Hot plug). This is important because many high-end servers, such as ones servicing a high volume web portal, cannot tolerate any down time because users are sending large numbers of requests to the server every second of the day.
It is critical that power to the PCI slot be turned off or disabled during installation or removal of a PCI card. If power to the PCI slot is not disabled, then a high transient Is voltage and a high voltage imbalance may occur when the contacts of the PCI card and PCI slot are pulled or pushed together. Unleashing such uncontrolled voltages would be uextremely undesirable, particularly for a high-end server. Electric currents generated by the voltages would likely cause damage not only to the PCI card, but also to other components on the motherboard. Voltage transients can also be induced to the signal bus and create data errors. Because PCI cards are installed and uninstalled by hand, a mechanism must be provided to ensure that power is disabled to a particular PCI slot before installation or uninstallation of a PCI card.
FIG. 1 is an illustration of a conventional hot swap system 10 known in the art that ensures power is disabled to a slot before removal of a card. Hot swap system 10 includes a chassis frame 12 having a slot 14 for receiving a card 16 (such as a PCI card for a hot swap PCI (HSPCI) system). A rocker 18 in a closed state secures card 16 to slot 14 by a rocker 18 (as shown). Rocker 18 includes a hinge 20 and a ridge 22 as well as a lock closed mechanism. Rocker 18 is rotably coupled to chassis frame 12 with hinge 20. Hot swap system 10 also includes a printed circuit board (PCB) 24 coupled to chassis frame 12. PCB 24 includes a mechanical switch 26 and may include indicator lights.
To install or uninstall card 16 from slot 14, a user must unlatch the lock mechanism and rotate rocker 18 about hinge 20 to an open state as shown by an arrow 28. The rotation of rocker 18 forces ridge 22 to depress mechanical switch 26. When mechanical switch 26 is actuated, the logic in PCB 24 or the chipset, disables power to slot 14. Therefore, hot swap system 10 releases card 16 and cuts the power to slot 14 at the same time. By ensuring that the power is disabled before card 16 is installed or uninstalled from slot 14, hot swap system 10 prevents damage to card 16 and other computer components from transient and imbalanced voltages as described above.
One problem with hot swap system 10 is that mechanical switch 26 has a physical connection to rocker 18 and prone to being unreliable. For example, if a user flips rocker 18 to an open state too quickly, mechanical switch 26 may snap from the excessive friction and pressure applied by ridge 22. Furthermore, mechanical switch 26 may become prone to breaking over time from being pressed too many times by ridge 22. Mechanical switch 26 is susceptible to switch intermittence if the computer system experiences any vibrations or shock (e.g., from user loading). Mechanical switch 26 is also susceptible to oxidation over time, which could make mechanical switch 26 more difficult to press down.
While efforts have been taken to improve the quality of mechanical switch 26, the failure rate of conventional hot swap system 10 is still unacceptable, particularly in high-end applications. If a card is removed from a slot while the power is still turned on, the damage to the computer system could be very costly. Furthermore, in a high-end system, such as a server powering an active commercial web site, any down time for the server is undesirable, especially if it is necessitated simply because of a mechanical switch failure. Therefore, it is desirable to have a method and apparatus that disables power prior to the installation or removal of a card with virtually no failures.